That was a blow to the Government efforts to calm mounting criticisms of the deal, seen by some as "monetary financing," the term used to describe direct financial support for Governments by the ECB, which banned under European law.

In its monthly report the Bundesbank appears to cast doubts on the legitimacy of the deal.

"The procedure proves the increasingly stronger and more problematic inter-linkage between monetary and fiscal policy in the European monetary union," the Bundesbank said.

"The European Stability Mechanism, which should be responsible in this regard, has been established to provide any help to individual member states in servicing debt."